This invention relates to fluid filtration devices of the type wherein a fluid-permeable filter media is operably disposed in flow-through filtering relationship with a fluid medium, and more particularly to an air filtration device constructed for use with the air intake manifold of an internal combustion engine such as reciprocating piston and rotary engines, such as those used in automobiles, trucks, motorcycles, small engine vehicles and lawn and garden engine-powered appliances, as well as larger turbine engines used on tanks, helicopters and the like, and power generating station gas turbines.
There are many types of air filtration devices for internal combustion engines on the market today. One example is an automotive air filtration unit offered on the Ford Mustang model year 2000 in which a rectangular cross section housing is provided at the upstream inlet end of the engine air intake manifold located on the left side fender well under the hood of the vehicle. This box-like housing has disposed within it an air filtration element in the form of a frustoconically shaped filter media with a blunt, imperforate nose of say three inches in diameter at its leading end. This filter media diverges from its nose in a conical shape with a straight taper to a diameter of about four or five inches at its rear end, and is approximately six to seven inches long. The conical surface of this filter is pleated, and the smaller diameter, blunt nose of the filter media is oriented as the leading end of the filter, thus facing upstream in the air flow stream being engine-drawn into the intake manifold.
One of the problems discovered with this prior art filter is caused by the nonconformance geometrically between the general conical shape of the filter media versus the generally rectangular shape of the enclosing housing. This configuration presents a relatively high level of air deflection and creates turbulence and eddies that also contribute to deposit collection of contaminating particles in certain areas of the housing, thereby reducing the efficiency of the filter relative to air flow capacity. Also, the audible noise level associated with such air filtration devices is objectionably high in some instances and under certain conditions. The aforementioned filter-housing configuration also reduces the air flow velocity through the filter due to the air flow deflections and turbulence effects. Conditions of velocity changes in air flow, depending on the engine demand, also typically change the interface angle between the impinging air and the filter surface, further reducing optimum performance of the filter.
Other examples of prior art automotive air filtering devices are those shown in the U.S. design patents DES. No. 401,597; DES. No. 401,942; DES. No. 403,414 and DES. No. 403,416.
Accordingly, among the objects of the present invention are to provide an improved air filtration method and device for performing such method, and an improved method of making such devices for use with internal combustion engines that achieves increasing air flow and air velocity through the air filtering system while maintaining a high level of air filtration, that operates with a lower level of air deflection in the air stream presented to the filter media due to unique and cooperative geometrical shapes of the filter media and the enclosing housing, wherein such cooperative shapes also create several thousand direct paths for the air to flow through the filter media without deflection, that enhances proper air flow direction and obtains higher operating air velocities than conventional air filtration devices, that reduces the audible noise level from that associated with prior air filtration devices, and which is simple and economical in construction, reliable in operation which provides a long service life.
In general, and by way of summary description and not by way of limitation, the present invention accomplishes one or more of the foregoing objects by providing an improved air filtration method and device for filtering solid contaminants from a stream of flowing fluid wherein a housing is provided having a tubular inlet exiting at its downstream end into a conically divergent first wall section having a first taper angle of divergence and terminating in a maximum diameter apex. The housing wall taper then reverses and thus continues in a convergent second wall section having a second angle of taper. The second wall section terminates at a housing outlet opening of greater diameter than the diameter of the inlet opening at the tubular inlet. A filter element is disposed within the interior chamber defined by the conical portions of the housing and has an exterior configuration generally complimental to that of the interior of the housing. The filter element thus has a first generally conical section divergent at a third taper angle greater than the first taper angle of the housing and a second generally conical downstream section convergent at a fourth taper angle from a maximum diameter apex of the filter to an outlet at an angle of convergence less than the second taper angle.
The filter housing and filter element thereby define first and second frustoconical annular chambers of successively diminishing cross-sectional radial thickness in the direction of downstream fluid flow.
In one embodiment the housing is constructed of flexible material such as rubber or the like and is molded as a one-piece unit.
In another embodiment the housing comprises a two-piece unit with half sections that mate together along mounting flanges provided at the side edges of each of the half sections. The housing is made of a plastic material having at least semi-rigid characteristics with sufficient strength to withstand in operation substantial pressure differences between that of the interior air stream and the exterior ambient atmosphere.
In both embodiments the filter element is radially corrugated to provide axially extending corrugations spaced generally uniformly around the entire circumference of the filter element and extending substantially for its entire axial length.